1. Field of the Invention
The instant invention relates to a beverage machine, in particular to a fully automatic coffee machine, comprising a main flow path that leads through a heating device, and a bypass flow path that circumvents the heating device.
2. Description of the Related Art
In beverage machines, the necessary brewing water, tea or also mixed infusion beverages are heated in heating devices, which are mostly set to a certain temperature. This temperature is set, e.g., in a boiler system as setpoint temperature or is predetermines by the system (e.g. water in a continuous-flow water heater system within a steam boiler). To be able to guarantee a consistently high quality of the beverage, it should be possible to individually dispense the optimum brewing water temperature for the beverage, for the purpose of which there are on principle three known possibilities. The first possibility is to heat the brewing water to the lowest required temperature and then to raise the system temperature briefly, based on the beverage, or to raise the beverage to the setpoint temperature by means of a downstream “booster” (small continuous-flow water heater). A second possibility is to provide the brewing water at a higher or at the highest necessary brewing temperature level in the heater system and then to set the desired brewing temperature by adding cold water. The third possibility is to heat the entire heater system very quickly based on the product. This, however, only seems sensible in the case of comparatively small dispensing quantities. Typically, the second possibility is used, that is, cold water is supplied to the actual heater system and the temperature is regulated through this. Either a cover or a magnetic valve is arranged in a bypass to release the bypass as needed and to allow cool water to flow to the beverage outlet around the heating device. The disadvantage of the mentioned systems is that it is not accurately known, which flow is set via the main path (heating device) and the bypass (cover/valve), because the pressure difference in both paths is approximately the same. In addition to the actual cross section of the two paths, the flow that occurs is a function of the flow speed, the hydrodynamics of the entire system as well as the viscosity of the medium. The occurring flow speed, in turn, varies highly as a function of the brewing device, which is connected downstream, or as a function of in which phase of preparation the system currently is (brewing start, preinfusion, brewing end, . . . ). The flow speed obviously also changes in the respective path, provided that it is turned off completely, for example by means of a valve. Unknown and uncontrollable impacts to the hydrodynamics also hold great uncertainties in terms of a mixing temperature that is to be set.
The instant invention deals with the problem of specifying an improved or at least an alternative embodiment for a beverage machine of the generic type that is characterized by a simple design solution, and that additionally provides reliable setting of an accurate mixing temperature.